Correlations and realistic interactions in doubly closed shell nuclei

We review the latest variational calculations of the ground state properties of doubly closed shell nuclei, from $^{12}$C to $^{208}$Pb, with semirealistic and realistic two- and three-nucleon interactions. The studies are carried on within the framework of the correlated basis function theory and integral equations technique, with state dependent correlations having central and tensor components. We report results for the ground state energy, one- and two-body densities and static structure functions. For $^{16}$O and $^{40}$Ca we use modern interactions and find that the accuracy of the method is comparable to that attained in nuclear matter with similar hamiltonians, giving nuclei underbound by $\sim$2 MeV/A. The computed Coulomb sums are in complete agreement with the latest analysis of the experimental data.Comment: 11 Latex pages, 2 ps figures. Talk delivered at the 10th International Conference on Recent Progress In Many-Body Theories, Seattle 1999. To appear in "Advances in Quantum Many-Body Theory", vol.3, World Scientifi

Extremal Hairy Black Holes

We consider a gravitating system consisting of a scalar field minimally coupled to gravity with a self-interacting potential and an U(1) electromagnetic field. Solving the coupled Einstein-Maxwell-scalar system we find exact hairy charged black hole solutions with the scalar field regular everywhere. We go to the zero temperature limit and we study the effect of the scalar field on the near horizon geometry of an extremal black hole. We find that except a critical value of the charge of the black hole there is also a critical value of the charge of the scalar field beyond of which the extremal black hole is destabilized. We study the thermodynamics of these solutions and we find that if the space is flat then at low temperature the Reissner-Nordstr\"om black hole is thermodynamically preferred, while if the space is AdS the hairy charged black hole is thermodynamically preferred at low temperature.Comment: 17 pages. Match with the journal version accepted by JHEP. arXiv admin note: substantial text overlap with arXiv:1309.216

Strong flavour changing effective operator contributions to single top quark production

We study the effects of dimension six effective operators on the production of single top quarks at the LHC. The operator set considered includes terms with effective gluon interactions and four-fermion terms. Analytic expressions for the several partonic cross sections of single top production will be presented, as well as the results of their integration on the parton density functions.Comment: 20 pages, 7 fig

Hawking radiation and propagation of massive charged scalar field on a three-dimensional G\"{o}del black hole

In this paper we consider the three-dimensional G\"{o}del black hole as a background and we study the vector particle tunneling from this background in order to obtain the Hawking temperature. Then, we study the propagation of a massive charged scalar field and we find the quasinormal modes analytically, which turns out be unstable as a consequence of the existence of closed time-like curves. Also, we consider the flux at the horizon and at infinity, and we compute the reflection and transmission coefficients as well as the absorption cross section. Mainly, we show that massive charged scalar waves can be superradiantly amplified by the three-dimensional G\"{o}del black hole and that the coefficients have an oscillatory behavior. Moreover, the absorption cross section is null at the high frequency limit and for certain values of the frequency.Comment: 18 pages, 12 figures. Accepted for publication in General Relativity and Gravitatio

PhD supervisors and faculty members might help to avoid burnout as well as enhance engagement and organisational citizenship behaviour (OCB) among PhD students.

There has been increased interest in the wellbeing and mental health of postgraduate students in light of the recent portrayal of the academic career as overworked and isolated. Research points to PhD students as being particularly at risk, yet the factors that contribute to PhD students’ compromised wellbeing are unclear. In this study (N = 392), we combine the social cure approach in social psychology with advances in organizational psychology to investigate potential predictors of work-related wellbeing and organisational citizenship behaviour (OCB) among PhD studentsin the UK. In particular, we explore the relationships between social support, willingness to support others, clarity of role, group belonging, engagement, and burnout using structural equation modelling (SEM). Our results point to the importance of support provided by both the supervisor and faculty members in helping to avoid burnout and enhance engagement among students. We also found that students’ identification with supervisors and faculty members together with clarity of role are positively associated with students’ work-related well-being. Moreover, although particular processes differ for early vs. late stage PhD students, our findings suggest that support from faculty members is a key predictor of intentions to perform OCB. Thus, received support is positively related to performing OCB both directly and indirectly via a sense of identification with faculty members. We discuss the implications of our findings in relation to policies aiming at improving the well-being of PhD students

Motion and collision of particles near DST Black holes

We consider Deser-Sarioglu-Tekin (DST) black holes as background and we study such the motion of massive particles as the collision of two spinning particles in the vicinity of its horizon. New kinds of orbits are allowed for small deviations of General Relativity, but the behavior of the collision is similar to the one observed for General Relativity. Some observables like bending of light and the perihelion precession are analyzed.Comment: 21 pages and 10 figures. New versio

Quasinormal modes and Stability Analysis for 4-dimensional Lifshitz Black Hole

We study the Lifshitz black hole in 4-dimensions with dynamical exponent z=2 and we calculate analytically the quasinormal modes of scalar perturbations. These quasinormal modes allows to study the stability of the Lifshitz black hole and we have obtained that Lifshitz black hole is stable.Comment: 7 pages, 2 figures. arXiv admin note: text overlap with arXiv:1205.058